The present application claims priority from Japanese Application No. P2000-300973 filed Sep. 29, 2000, the disclosure of which is hereby incorporated by reference herein.
The present invention relates to a memory apparatus and a memory access restricting method using a reversibly non-writable memory.
A reversibly non-writable memory in which data can be written one time is known. For example, as a semiconductor memory, so-called OTP (One Time Programmable ROM) in which data can be written one time has been proposed. The related art reference is a non-volatile reversibly non-writable memory. In other words, according to the related art reference, once data is written, it cannot be erased. Thus, even if the power of the memory is turned off, written data is kept retained. The reversibly non-writable memory can be fabricated at a lower cost than the flash memory.
Recently, the commercial use of the card type flash memories as data record mediums has tended to increase. For example, still pictures photographed by a digital camera are recorded to a flash memory. To protect the privacy of the user, it is necessary to improve the secrecy of data recorded in a flash memory.
As another problem of the flash memory, the cost thereof is relatively high.
Therefore, an object of the present invention is to provide a memory apparatus and an access restricting method that allow the secrecy of data written thereto to be improved using a characteristic of a reversibly non-writable memory.
To solve the above-described problem, a first aspect of the present invention is a memory apparatus including a reversibly non-writable memory having a designated area and other areas, a detecting unit operable to determine whether the designated area of the memory is in an initial state, and a controller operable to permit access to the designated area and the other areas of the memory when the detecting unit determines that the designated area is in the initial state, and to prohibit access to the designated area and the other areas of the memory when the detecting unit determines that the designated area is not in the initial state.
A second aspect of the present invention is a method for restricting access to a reversibly non-writable memory apparatus, including determining an access state of the memory apparatus; when the memory apparatus is in an access-restricted state, changing the access state of the memory apparatus to an access-permitted state; and when the memory apparatus is in the access-permitted state, changing the access state of the memory apparatus to the access-restricted state.
According to the present invention, when the designated area is in an initial state, the area is not access-restricted. When the designated area is not in the initial state, the area can be access-restricted. When the area has been access-restricted, the area can be changed to the access permitted state.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.